I walk through an idea from one of my idea notebooks, explaining how to expand it into a design for setting, story, and system mechanics, as well as how I would pitch it to publishers and how I would evaluate its merits.
Videos I reference:
Making And Maintaining An IP: https://www.youtube.com/watch?v=waUjJ2VjvaE
How To Make A Good Game Setting: https://www.youtube.com/watch?v=kW7gOPHmr-Q
How To Write Design Docs: https://www.youtube.com/watch?v=ohHLUKj3NTk